1. The Field of the Invention
The present invention relates generally to reforming nanocatalysts and methods for making and using such catalysts. Such reforming catalysts include supported nanocatalyst particles and are used for the reforming of naphtha and formation of BTX.
2. The Relevant Technology
Naphtha is a volatile, flammable liquid mixture of hydrocarbons distilled from petroleum or other fossil fuel sources. Naphtha can be used as a fuel, a solvent, or in making various chemicals. Typically naphtha is a mixture of hydrocarbons that boil between about 65° C. and about 195° C. and is obtained from processing crude oil and heavy oil fractions.
Catalytic naphtha reforming is an important petroleum refining operation. In catalytic naphtha reforming, a catalyst is used to reform the naphtha to make more valuable hydrocarbon products.
For example, a reforming catalyst can be used to increase the octane number of a naphtha mixture, thereby making it more suitable for gasoline blending. The reformed product, or reformate, is one of the two most important contributors to the motor gasoline pool. Octane number gains by catalytic reforming vary depending on the feed quality and the reaction conditions, but typically range between 30 and 70.
Another application of naphtha reforming is the production of benzene, toluene, and xylenes, also known collectively as BTX. These compounds, while useful for increasing octane, also have significant value and uses in various chemical industries. When reforming is optimized to produce benzene, toluene, xylenes, ethyl benzene, and other aromatic compounds, the reforming procedure is called a BTX operation.
An additional benefit of naphtha reforming is the production of hydrogen. Hydrogen is used in many other refining operations, and naphtha reforming is typically the only refining process with a net production of hydrogen.
Catalytic naphtha reforming usually includes a number of different reactions that take place in the vapor phase over a suitable catalyst. Important reforming reactions include: dehydrogenation of naphthenes to produce aromatics, isomerization of linear paraffins to form branched paraffins or iso-paraffins, and dehydrocyclization of paraffins to form aromatics.
Each reaction can be favored by somewhat different reaction conditions and can take place at different catalytic active sites. Some of these reactions, such as dehydrogenation, are catalyzed by metal sites, whereas others, such as isomerization and dehydrocyclization, take place mostly via a bifunctional mechanism, meaning they require both metal and acid catalytic sites.
Undesirable reactions can also occur. Examples of undesirable reactions include coking, which can deactivate the catalyst, and hydrogenolysis, which is a highly exothermic reaction that produces light hydrocarbon gases from larger paraffins.
Hydrocracking is another reaction that can occur during naphtha reforming. Hydrocracking involves the cleavage of a C—C bond, resulting in the formation of lighter paraffins from heavier ones and in ring opening in naphthenes. For some hydrocarbon molecules hydrocracking is desirable, while for others it is not. Nevertheless, it usually occurs to some extent under typical reforming conditions.
Naphtha reforming catalysts are designed to minimize undesired reactions, deactivate slowly, and show high activity and selectivity toward desired products. To achieve these properties, naphtha reforming catalysts are typically made from precious metals such as platinum.
Because current reforming catalysts are made with very expensive metals such as noble metals, there is a need to increase the activity, selectivity and long-term stability of reforming catalysts. While many improvements have been made to reforming catalysts in recent years, there is still a need to further improve the activity, selectivity, and stability of these and other catalysts to reduce the costs of reforming procedures.